X0306 4 2018-05-17 false 0001656328 Sienna Biopharmaceuticals, Inc. SNNA 0001573074 Beddingfield III Frederick C/O SIENNA BIOPHARMACEUTICALS, INC. 30699 RUSSELL RANCH ROAD, SUITE 140 WESTLAKE VILLAGE CA 91362 true true false false President & CEO Common Stock 2018-05-17 4 J false 47594.00 A 601246.00 D Common Stock 14076.00 I See Footnote Common Stock 14076.00 I See Footnote Common Stock 112614.00 I See Footnote Dr. Beddingfield acquired the shares pursuant to a mandatory distribution from Venvest Biotech, LLC ("Venvest") for which Dr. Beddingfield has a previously disclosed economic interest in any gain associated with the shares of the Issuer's capital stock purchased by Venvest in the Issuer's Series A-3 and Series B Preferred Stock financings. Dr. Beddingfield has no management or voting rights in respect of Venvest (Including no voting or investment power with respect to shares of the Issuer's capital stock held by Venvest). The shares are directly held by Beddingfield Children's Trust fbo Catherine Sara Beddingfield. The shares are directly held by Beddingfield Children's Trust fbo Claire Elizabeth Beddingfield. The shares are directly held by the Beddingfield Family Trust. /s/ Timothy K. Andrews, attorney-in-fact for Frederick C. Beddingfield III 2018-05-21